Current scientific review of the taxonomy of wild equids (Groves 1986) places Przewalski's Horse as a subspecies of the extinctEquus ferus. Although Przewalski's Horse (Equus ferus przewalskii) can hybridize with domestic horses (Equus ferus caballus) to produce fertile offspring (Ryderet al. 1978, Trommerhausen-Smithet al. 1979), the existence of 2n = 66 chromosomes in Przewalski's Horse identifies it as being more different from its domestic relatives (2n = 64) than are any two breeds of domestic horse (Ryder 1994). Furthermore, mitochondrial DNA research has shown that the Przewalski's Horse is not the ancestor of modern domestic horses (Vilàet al.2001). Przewalski's Horse also show a number of consistent differences in their appearance as compared to domestic horse breeds: the mane is short and erect when in good body condition; forelocks are nearly nonexistent; the upper part of the tail has short guard hairs; a dark dorsal stripe runs from the mane down the spine to the tail; several dark stripes can be present on the carpus and generally the tarsus (Groves 1994). Przewalski's Horses grow a thick mane in winter, which contrary to domestic horses they shed each spring with the rest of their winter coat.

Other studies of the genetic differences between Przewalski's and domestic horses have indicated very little genetic distinction between them. Only four alleles at four separate serological marker loci have been identified as specific to Przewalski's Horse (Bowling and Ryder 1987); the vast majority of blood protein variants are present in both Przewalski's and domestic horses and even the fastest evolving DNA region known in mammals (the mitochondrial DNA control region), does not show significant differences between the two types of horse (Ishidaet al.1995, Oakenfull and Ryder 1998). Thus it is clear that Przewalski's and domestic horses are very closely related and have in the past interbred, but the fixed chromosomal number difference between them indicates that they are distinct populations (Oakenfullet al.2000). A variety of molecular studies support their phylogenetic relationship as sister taxa (Steineret al.2012, Côtéet al.2013) diverging between 150,000 and 250,000 years ago (Gotoet al.2011, Steiner and Ryder 2011).

Justification:
Previously listed as Extinct in the Wild (EW) from the 1960s up to the assessment in 1996. The species was then reassessed as Critically Endangered (CR) due to at least one surviving mature individual in the wild. Successful reintroductions have qualified this species for reassessment. The population is currently estimated to consist of more than 50 mature individuals free-living in the wild for the past seven years. This taxon is threatened by small population size and restricted range, potential hybridization with domestic horses, loss of genetic diversity, and disease. As the population size is small, it is vulnerable to stochastic events such as severe weather. Equus ferus przewalskii qualifies as Endangered (EN) under Criterion D.

Until the late 18th century, this species ranged from the Russian Steppes east to Kazakhstan, Mongolia and northern China. After this time, the species went into catastrophic decline. The last wild population of Przewalski’s Horse (Equus ferus przewalskii) survived until the mid-20th century in southwestern Mongolia and adjacent Gansu, Xinjiang, and Inner Mongolia (China). Wild horses were last seen in 1969, north of the Tachiin Shaar Nuruu in Dzungarian Gobi Desert in Mongolia (Paklina and Pozdnyakova 1989).

All extant wild horses belong to the subspecies Equus ferus przewalskii. The first visual account of Przewalski's-type wild horses date from more than 20,000 years ago. Rock engravings, paintings, and decorated tools dating from the late Gravetian to the late Magdalenian (20,000-9,000 BC), were discovered in caves in Italy, southern France, and northern Spain; 610 of these were horse figures (Leroi-Gourhan 1971). Many cave drawings in France show horses that look like Przewalski’s Horse (Mohr 1971). In prehistoric times, the species probably roamed widely over the steppes of Central Asia, China, and Europe (Ryder 1990), although wild horses in Europe could have been Tarpans (Equus ferus gmelini).

The first written accounts of Przewalski's Horse originate from Tibet, recorded by the monk Bodowa, who lived around 900 AD. In the "Secret History of the Mongols", there is also a reference to wild horses that crossed the path of Chinggis Khaan during his campaign against Tangut in 1226, causing his horse to rear and throw him to the ground (Bokonyi 1974). That the wild horse was a prestigious gift, denoting its rarity or that it was difficult to catch, is shown by the presentation of a Przewalski’s Horse to the emperor of Manchuria by Chechen-Khansoloj-Chalkaskyden, an important Mongolian, circa 1630 (Zevegmid and Dawaa 1973). In a Manchurian dictionary of 1771, Przewalski’s Horse is mentioned as "a wild horse from the steppe" (Dovchin 1961).

Przewalski's Horse was not described in Linnaeus's "Systema Naturae" (1758) and remained largely unknown in the West until first mentioned by John Bell, a Scottish doctor who travelled in the service of Tsar Peter the Great in 1719-1722 (Mohr 1971). His account of the expedition, "A Journey from St Petersburg to Peking", was published in 1763. Bell and subsequent observers all located horses known at that time within the area of 85-97°E and 43-50°N (Chinese-Mongolian border). Wild horses were reported again from what is now China by Colonel Nikolai Mikailovich Przewalski, an eminent explorer, at the end of the 19th century. He made several expeditions by order of Tsar Alexander the Second of Russia to Central Asia, aiming to reach Tibet. While returning from his second expedition in Central Asia, he was presented with the skull and hide of a horse shot about 80 km north of Gutschen (in present-day China, around 40°N, 90°E). The remains were examined at the Zoological Museum of the Academy of Science in St Petersburg by I.S. Poliakov, who concluded that they were a wild horse, which he gave the official name Equus przewalskii (Poliakov 1881). Further reports came from the brothers Grigory and Michael Grum-Grzhimailo, who travelled through western China from 1889-1890. In 1889, they discovered a group in the Gashun area and shot four horses: three stallions and a mare. The four hides and the skulls of the three stallions, together with an incomplete skeleton, were sent back to the Zoological Museum in St. Petersburg. They were able to observe the horses from a short distance and gave the following account: "Wild horses keep in bands of no more than ten, each herd having a dominant stallion. There are other males, too, but they are young and, judging by the hide of the two-year old colt that we killed, the dominant male treats them very cruelly. In fact, the hide showed traces of numerous bites" (Grum-Grzhimailo 1982).

After the 'rediscovery' of the Przewalski's Horse for western science, western zoos and wild animal parks became interested in this species for their collections. Several long expeditions were mounted to catch animals. Some expeditions came back empty-handed and some had only seen a glimpse of wild Przewalski's Horses. It proved difficult to catch adult horses, because they were too shy and fast. Capture of foals was considered the best option as when chased they would become exhausted and lag behind their group (Hagenbeck 1909), although this may have involved killing adult harem members in the process (Bouman and Bouman 1994). Four expeditions that managed to catch live foals took place between 1897 and 1902. Fifty-three of these foals reached the west alive. Between the 1930s and the 1940s only a few Przewalski's Horses were caught and most died. One mare (Orlitza III) was caught as a foal in 1947 and was the last wild mare to contribute to the Przewalski's Horse gene pool in Europe. In Mongolia several Przewalski's Horses were captured and crossbred with domestic horses by the Mongolian War Ministry (Bouman and Bouman 1994).

In subsequent years the captive population increased, and since the 1990s reintroduction efforts have started in Mongolia and China; Mongolia was the first country where truly wild reintroduced populations existed within the historic range. Reintroductions in Mongolia began in the Great Gobi B Strictly Protected Area in the Dzungarian Basin (9,000 km2) and Hustai National Park in Mongol Daguur Steppe (570 km2) in 1994 (King and Gurnell 2005). A third reintroduction site, Khomintal, (2,500 km2), in the Great Lakes Depression, was established in 2004, as a buffer zone to the Khar Us Nuur National Park in Valley of the Lakes (C. Feh pers. comm.). Releases began in the Kalamaili Nature Reserve (17,330 km2), Xinjiang Province, China in 2001 and in the Dunhuang Xihu National Nature Reserve (6,600 km2), Gansu Province, China in 2010 (Liu et al. 2014), although almost all of these animals are corralled and fed in winter (Qing Cao pers. comm.). Further reintroduction sites are planned in Kazakhstan and Russia (W. Zimmerman pers. comm.).

The history of population estimates and trends in the Przewalski's Horse has been described by Wakefield et al. (2002). Small groups of horses were reported through the 1940s and 1950s in an area between the Baitag-Bogdo ridge and the ridge of the Takhin-Shaar Nuruu (which translated from Mongolian, means 'Yellow Mountain of the Wild Horse'), but numbers appeared to decline dramatically after World War II. The last confirmed sighting in the wild was made in 1969 by the Mongolian scientist N. Dovchin. He saw a stallion near a spring called Gun Tamga, north of the Takhin-Shaar Nuruu, in the Dzungarian Gobi (Paklina and Pozdnyakova 1989). Subsequent annual investigations by the Joint Mongolian-Soviet Expedition failed to find conclusive evidence for their survival in the wild (Ryder 1990). Chinese biologists conducted a survey in northeastern Xinjiang from 1980 to 1982 (covering the area of 88-90°E and 41°31'-47°10'N) without finding any horses (Gao and Gu 1989). The last native wild populations had disappeared.

Of the 53 animals recorded in the Studbook as having been brought into zoological collections in the west, fewer than 25% contributed any genes to the current living population. All Przewalski's Horses alive today are descended from 12 wild-caught individuals, and as many as four domestic horse founders described below, which were the nucleus of the captive breeding programme (Bowling and Ryder 1987). Eleven of the wild-caught individuals were brought into captivity between 1899 and 1902 with the last of them dying in 1939. The twelfth founder (Orlitza III) was captured as a foal in 1947. A thirteenth founder was born in 1906 in Halle (Germany) to a wild-caught stallion and a domestic Mongolian mare, and a fourteenth founder is a female born in Askania Nova (Ukraine) to a Przewalski's Horse stallion and a domestic female of a Tarpan type. In spite of the introgression of domestic horse blood, the current population is genetically very close to the original wild horses (Bowling et al. 2003).

As of 1 January 2014, the number of living captive and reintroduced animals in the International Studbook was 1,988 (883 males.1101 females.4 sex unknown). In addition to animals held in captivity and those already re-introduced, there have been a number of animals released into very large enclosures (reserves): Le Villaret, France (~4 km2; 2013: 18.18), Askania Nova, Ukraine (30 km2; 2014: 24.46), and Hortobágy National Park, Hungary (700 km2; 2014: 125.129). Bukhara, Uzbekistan (51 km2) had 19.17.1 horses in 2008 (W. Zimmermann pers. comm.) and 24 horses by 2013 (O. Pereladova pers. comm.). The unfenced Chernobyl exclusion zone (2,600 km2) in Ukraine contained 32.36 horses in 2008 (W. Zimmermann pers. comm.), and approximately 60 horses in early 2014 (T. Mousseau pers. comm.).

There are now approximately 387 free-ranging reintroduced and native-born Przewalski's Horses in Mongolia at three reintroduction sites (Zimmerman 2014). Between 1992 and 2004, 90 captive-born horses were transported to the Takhin Tal acclimatization site, from where they were released into the Great Gobi B Strictly Protected Area (SPA) (ITG International Takhi Group, Zimmermann 2008). A further three males were translocated from Hustai National Park to Takhin Tal in 2007 (Zimmermann 2008). In 2008 there were approximately 111 free-ranging horses in this subpopulation (Zimmerman 2008, Kaczensky and Walzer 2004). By December 2009 there were 138 individuals, but due to an extremely harsh winter (dzud) in 2009/2010 the population suffered extreme mortality: in April 2010 only 49 individuals remained (Kaczensky et al. 2011). By 2012 the population had increased to 71. By the end of 2013 there were 90 horses forming six harems and several bachelor groups. Sixteen foals were born in 2013; three of these foals died, and one adult male disappeared and is presumed dead (P. Kaczensky pers. comm.).

From 1992 to 2000, 84 horses were brought to Hustai National Park (NP) by the Foundation for the Preservation and Protection of the Przewalski Horse and Mongolian Association for Conservation of Nature and the Environment (MACNE) from reserves in Europe (King and Gurnell 2005). As of the middle of 2012 this population had approximately 275 individuals (Zimmerman 2014). By the end of 2013, there were 297 horses, of which 228 were members of 29 harems and the rest were bachelors. Sixty-four foals were born in 2013, with a 61% survival rate by year’s end: 25 foals, four yearlings, and seven adults died during 2013 (Usukhjargal 2013).

A third reintroduction site was started in 2004 at Seriin Nuruu in the Khomiin Tal buffer zone of the Khar Us Nuur National Park in western Mongolia (Association pour le Cheval de Przewalski: TAKH). Twenty-two individuals consisting of four pre-established families and one male bachelor group were brought from the reserve at Le Villaret, France between 2004 and 2005, and four horses from Prague Zoo were added in 2011 (Association TAKH, Zimmermann 2008). By the end of 2013 this population had 40 horses; eight foals were born in 2013 and 3threeof these died, as did two adult stallions (C. Feh pers. comm.).

In previous assessments of the reintroduced population in Mongolia, mature individuals were considered to be those that were born in the wild and five years of age. Individuals born in captivity were not counted as mature until they had reproduced in the wild, and produced offspring that were at least five years old (so potentially reproductive). The population grew from 55 mature individuals in the wild in 2006 (52: 26.26 in Hustai NP, 3: 1.2 in Gobi NP), to 79 in 2007 (Hustai NP: 33.35; Great Gobi B SPA: 3.8), 104 in 2008 (Hustai NP: 39.51; Great Gobi B SPA: 7.7), and 151 in 2009 (Hustai NP: 52.66; Great Gobi B SPA: 15.18). The winter of 2009/2010 was very severe and there was high mortality of Przewalski's Horses, particularly in the Gobi. In 2010, Hustai NP's mature population was 117 (53.64) and Great Gobi B SPA's number of mature individuals was reduced to 17 (8.9), giving a total population of 134 mature individuals. In 2012 the criterion for captive-born horses to be included as mature individuals was tightened to require them to have produced reproductively viable offspring (i.e., the reintroduced animal reproduced, and at least one of its offspring also reproduced); mature (≥5 years old) wild-born individuals continued to be included. Under these criteria, there were 178 mature individuals in the wild at the end of 2012: 153 (65.88) in Hustai NP, 23 (5.18) in Great Gobi B SPA, and 2 (1.1) in Khomiin Tal. Hence for a period of seven years, the mature population of Przewalski's Horses in Mongolia has been more than 50 individuals. Although this means that the Przewalski's Horse qualifies as Endangered (EN) it should be borne in mind that most of these individuals are from one reintroduction site and climatic perturbations like the extremely harsh winter in 2009/2010 can have very negative effects on small populations (Kaczensky et al. 2011). In China, the Wild Horse Breeding Centre (WHBC) in Xinjiang Province has established a large captive population of Przewalski's Horses (Liu et al. 2014). Since 2001 horses have been released into the nearby Kalamaili Nature Reserve (KNR), which had a population of 99 in 2012 and 121 in 2013. One harem group is roaming free on the Chinese side of the Dzungarian Gobi (Xinjiang); another 102 horses are roaming free during summer time but are returned to the acclimatization pen during the winter (Zimmermann et al. 2008; Qing Cao pers. comm.). The Gansu Endangered Species Research Center (GESRC) also has a captive breeding programme and has released at least seven horses into the Dunhuang Xihu National Nature Reserve (DXNNR) in 2010 and 2012 (Liu et al. 2014); all of these horses are fed in winter. A total of 59 foals have been born in the wild in China since 2009, with an estimated 19 individuals surviving in 2013 (Qing Cao pers. comm.). Until better data are available these animals are not known for sure to meet the criterion of mature individuals for a reintroduced species so have not been included in the species population size for this assessment.

Przewalski’s Horses exhibit a harem defense polygyny (Van Dierendonck et al. 1996). After dispersing from their natal band at approximately 2 years of age, males enter bachelor groups consisting of other young males and unsuccessful older stallions. When they are five years of age or older, stallions attempt to form harems of semi-permanent membership that are held year-round. They take over already-established harems, steal mares from rivals, or are joined by females dispersing from their natal harem at approximately two to three years of age (L. Boyd pers. comm.; Zimmermann et al. 2009).

Przewalski's Horse formerly inhabited steppe and semi-desert habitats. As most of this range became converted to agriculture, degraded or was increasingly occupied by livestock, the species became restricted to semi-desert habitats with limited water resources (Van Dierendonck and de Vries 1996). Lowland steppe vegetation was preferentially selected by horses at Hustai National Park and seasonal movements were affected by the availability of the most nutritious vegetation (King and Gurnell 2005). The breadth of species consumed and dietary overlap with other ungulates increased in winter, compared to summer, although forage did not appear to be limiting (Siestes et al. 2009). In the Gobi the Przewalski's Horses also selected for the most productive plant communities (Kaczensky et al. 2008).

The species is not territorial; home range sizes in Hustai NP varied from 120 to 2,400 ha and, in addition to grazing sites, included a permanent water source, patches of forest, and ridges with rocky outcrops (King and Gurnell 2005). In Great Gobi B SPA, home ranges of 150 to 825 km2 were reported (Kaczensky et al. 2008).

Because the historic range is not precisely known, there has been much debate about the areas in which Przewalski's Horses were last seen: was it merely a refuge or was it representative of the typical/preferred habitat? The Mongolia Takhi Strategy and Plan Work Group (MTSPWG 1993) concluded that the historic range may have been wider but that the Dzungarian Gobi, where they were last seen, was not a marginal site to which the species retreated as they had access to the rich habitats of mountain valleys and more oases than in the present time (Sokolov et al. 1990), due to these areas being occupied by herders and their livestock. Although grass and water are more available in other parts of Mongolia, these areas often have harsher winters. Subsequently, others provided evidence that the Gobi is an edge habitat, rather than an optimal habitat for Przewalski's Horses (Kaczensky et al. 2008), and certainly also subject to severe winters with devastating consequences for the population (Kaczensky et al. 2011). Studies of feral horses have shown that they are able to live and reproduce in semi-desert habitats but their survival and reproductive success is clearly sub-optimal compared to feral horses on more mesic grassland (Berger 1986). Van Dierendonck and de Vries (1996) suggest that the wild horse is primarily a steppe herbivore that can survive under arid conditions when there is access to waterholes.

There is currently no use or trade in Przewalski's Horses. Hunting is not currently a threat to the species, though this needs to be monitored. It is believed that capture of animals for cross-breeding as racehorses is a potential future use, and threat.

A number of causes have been cited for the final extinction of Przewalski's Horses in Mongolia and China. Among these are significant cultural and political changes (Bouman and Bouman 1994), hunting (Zhao and Liang 1992, Bouman and Bouman 1994), military activities (Ryder 1993), climatic change (Sokolov et al. 1992), and competition with livestock and increasing land use pressure (Sokolov et al. 1992, Ryder 1993, Bouman and Bouman 1994). Capture expeditions probably diminished the remaining Przewalski's Horse populations by killing and dispersing the adults (Van Dierendonck and de Vries 1996). The harsh winters of 1945, 1948, and 1956 probably had an additional impact on the small population (Bouman and Bouman 1994). Increased pressure on, and rarity of waterholes in their last refuge should also be considered as a significant factor contributing to their extinction (Van Dierendonck and de Vries 1996).

For the reintroduced populations, small population size and limited spatial distribution is the primary threat, followed by potential hybridization with domestic horses and competition for resources with domestic horses and other livestock. Wherever Przewalski's Horses come into contact with domestic horses, there is the risk of hybridization and transmission of diseases. Recently, illegal mining in the protected areas is an additional threat to their viability. In Hustai NP it has been noted that overgrazing of the buffer-zone and continued pressure on the reserve are possible consequences of the enhanced economic activity in this area (Bouman 1998); however, the second phase of the project (1998-2003) paid much more attention to sustainable development of the buffer-zone. In the western section of the Great Gobi B SPA livestock grazing by nomads and military personnel continues, particularly in fall, winter and spring; however, the core zone is largely free from human influence all year round. Infectious diseases transmitted from domestic horses and their parasites, notably Babesia equi, B. caballi and strangles (infection by Streptococcus equi), are a major threat to small reintroduced populations originating from zoos (Roberts et al. 2005, King and Gurnell 2005). As was observed during 2009/2010, severe winters can result in significant mortality. While predation occurs naturally as for any wild ungulate, if excessive there could be impacts on this small population.

There is concern over loss of genetic diversity after being reduced to a very small population and maintained in captivity for several generations. Sixty per cent of the unique genes of the studbook population have been lost (Ryder 1994). Loss of founder genes is irretrievable and further losses must be minimized through close genetic management. Furthermore, inbreeding depression could become a population-wide concern as the population inevitably becomes increasingly inbred (Ballou 1994). However, correct management of the population can slow these losses significantly, as has been achieved since the organization of the regional captive-breeding programs. Fortunately, Przewalski's Horses have been shown to have both higher nuclear and mitochondrial nucleotide diversity than many domestic horse breeds in spite of the population bottlenecks they have experienced (Goto et al. 2011).

At the ‘Endangered Wild Equid Workshop’ held in Ulaanbataar in 2010 the following threats were identified:Loss of population due to stochastic events (i.e. severe winter);

Limited habitat and resources (pasture and water);

Domestic horses (hybridization, disease, social stress);

Lack of information, appreciation / awareness, lack of knowledge; and

Exploitation of resources (i.e. mining).

Specific actions needed for each threat category were identified and described.

Przewalski's Horse is legally protected in Mongolia. It is protected as Very Rare under part 7.1 of the Law of the Mongolian Animal Kingdom (2000). Hunting has been prohibited since 1930, and the species is listed as Very Rare under the 1995 Mongolian Hunting Law (MNE 1996). It is listed as Critically Endangered in both the 1987 and 1997 Mongolian Red Books (Shagdarsuren et al. 1987, MNE 1997), and in the Regional Red List for Mongolia (Clark et al. 2006). The taxon's re-introduced range in Mongolia is almost entirely within protected areas. It is listed on CITES Appendix I (as Equus przewalskii).

The following conservation actions are in place:

An International Studbook was produced in 1959, followed in the 1970s by establishment of the North American Breeders Group, which developed into the Species Survival Plan for the Przewalski's Horse. The European Endangered Species Programme for this species was accepted in 1986. Many countries now cooperate in these programmes to minimize inbreeding and retain genetic diversity in their horse populations.

There are three reintroduction sites in Mongolia, plus two in China.

The Status and Action Plan for the Przewalski's Horse (Equus ferus przewalskii) was produced in 2002 (Wakefield et al. 2002), and provides a more detailed account of the history and ongoing conservation efforts surrounding the species.

All three Mongolian reintroduction sites are monitoring their populations and are integrating community livelihood support into their projects (Ulambayar 2004).

There have been several workshops of stakeholders involved in the reintroduction of Przewalski's Horse to Mongolia (Boyd 2009).

Conservation actions required:

The health of wild and domestic horses should be monitored for disease (Roberts et al. 2005). Standardized techniques should be used to monitor health, fecundity, mortality, habitat utilization and social organization of all populations (Wakefield et al. 2002).

Contact between Przewalski's Horses and domestic horses should be kept to a minimum.

A single population management approach should be developed.

Mongolia currently has the only sizeable wild population and an action plan is needed for the country.

The genealogy of all horses in Mongolia should be established based on individual genotypes from micro-satellite data to monitor inbreeding levels, identify hybrids and plan for necessary movements of horses between reintroduction centres to maximize genetic diversity.

An authoritative government protocol for hybrids should be developed, to be established before hybridization occurs, and to be made available in each re-introduction centre and to local people (King and Gurnell 2005).

Further communication and cooperation between all re-introduction centres would be beneficial.

Further training and post-graduate education of staff and biologists involved with this conservation work would be beneficial.

Websites for the reintroduction sites in Mongolia with further details and ways of supporting them are: